1. Field of the Invention
This invention relates to gas turbine engine air cooled blade members and, more particularly, to an improved method and replacement member for repairing such a member in the area of its edge portions.
2. Description of the Prior Art
Blade members used in the turbine section of gas turbine engines experience strenuous operating conditions including a combination of mechanical stresses, thermal stresses and rotational stresses resulting from rapid spinning in the hot gas stream. As a result, such blade members have been designed to be air cooled to enable utilization of increased material properties. A variety of such blade members have been described in the art, one example of which is U.S. Pat. No. 3,628,885-Sidenstick et al patented Dec. 21, 1971, assigned to the assignee of the present invention and the disclosure of which is incorporated herein by reference. These types of blade members include a hollow interior portion enclosed by walls, some of which include openings to allow cooling air to exit from within the hollow interior of the blade member. In addition, such air cooled blade members include edge chambers, such as along the leading edge or trailing edge or both, extending along the length of the airfoil and extending chordwise into the airfoil toward the other edge to a longitudinally extending chamber wall which separates the edge chamber from the interior of the blade member.
As is shown in the above-incorporated Sidenstick et al patent and as can be appreciated from this kind of art, such blade members are complex in design and are relatively costly to manufacture. Therefore, it is desirable to repair rather than to replace such blade members which have been worn or damaged during gas turbine engine operation. For example, it has been recognized that a substantial portion of such wear or damage can occur at the leading edge wall by a combination of occurrences as impingement and thermal cracking, as well as at the trailing edge portions such as results from thermal cracking. Although repair of such a blade member has been made by fusion welding, such repair method has limitations because of distortion because of welding. In addition, recracking of the repair welds has been experienced in some instances. Other reported repair methods include that described in U.S. Pat. No. 4,098,450-Keller et al, patented July 4, 1978 assigned to the assignee of the present invention, the disclosure of which is incorporated herein by reference. Such repair method, however, is difficult to use with blade members which have experienced extensive damage and sometimes loss of substantial portions of the leading or trailing edges or both.